Method for monitoring communications in a cellular radiocommunication system, and network core therefor

ABSTRACT

The invention concerns a cellular radiocommunication system comprising a network core ( 21 ) including switches ( 28, 30, 32 ), one or several gateways ( 28, 32 ) to external networks, subscriber management means ( 33 ) and billing management means ( 34, 35 ). Several radio access networks ( 22, 40 ), including each base stations ( 24, 42 ) capable of radio communication with mobile stations ( 23 ), are connected to the network core switches. Said radio access networks include an access network ( 22 ) managed with the network core by a cellular operator and at least an additional access network ( 40 ) having a substantially less extensive radio coverage and a substantially wider bandwidth than the one managed by the cellular operator. When setting up a communication with a mobile station through the network core and one of the access networks, a report message is generated specifying the access network concerned.

The present invention concerns the management of cellularradiocommunication networks.

In conventional telecommunications systems, consisting of a set ofinterconnected networks, each of these networks being managed by asingle operator, each network gathers information on each serviceprovision to a subscriber, in order to calculate billing data. Thegathered information is then sorted based on the subscriber's identity,in order to debit the subscribers or organizations responsible fordebiting a subset of subscribers.

Wireless systems are examples of such interconnected networks. Onespecial feature is that under certain conditions a network subscribermay occasionally use the resources of another network. This is calledroaming.

Assuming that a subscriber of a network A, located within the coverageof another network B, makes a call or performs any other billabletelecommunications transaction, network B records the information onthis transaction with a subscriber identification, which in particularindicates his/her home network. Network B sorts these records based onsubscriber identities, and it builds a file for network A, which inparticular includes the record concerning the roaming subscriber.

If the interconnected networks A and B mutually call upon theirresources to route traffic, each network records data describing thetraffic to the other network, and cross billing is carried out bycomparing the traffic exchanged without referring to the subscribers'identities. This situation is typically that of international telephonetraffic.

This situation is also that of the interoperation of a private networkwith a public network. The public operator measures the trafficexchanged at a gateway between the two networks, and bills the privateoperator on this basis.

If network B belongs to a hierarchically higher layer than network A(e.g. A is a regional telephone company and B is the national operator),network A uses the resources of network B to route these communications.The operator of network A must then pay for the routing servicesprovided by network B.

In the field of cellular radiocommunication networks, the ETSI (EuropeanTelecommunications Standard Institute) has suggested interconnectinglarge coverage cellular public land mobile networks (PLMN) withbroadband radio access networks (BRAN).

The BRAN is typically a wireless local area network (WLAN) which can beof the HiperLAN/1 or HiperLAN/2 type according to ETSI standards. TheseHiperLAN networks are short range and operate in frequency bands around2.4 or 5.2 GHz. The ETSI recommends convergence protocols above theHiperLAN/2 protocols, for connecting these WLANs with more extensivenetworks, in particular cellular networks.

The aim is to allow WLAN subscribers to take advantage of the servicesoffered by the cellular network.

There are similar WLAN standards in the United States, namely standardsIEEE 802.11 b and IEEE 802.11 a.

An object of the present invention is to organize interoperation betweena cellular network and WLANs such that subscribers of the cellularnetwork may use the broadband resources of the WLAN.

The invention thus proposes a method for monitoring communications in acellular radiocommunication system comprising a core network includingswitches, at least one gateway to an external network, subscribermanagement means and billing management means, as well as a plurality ofradio access networks connected to the core network switches, eachincluding base stations capable of radio communication with mobilestations. The radio access networks include a first access networkmanaged with the core network by a cellular operator and at least onesecond access network having a substantially less extensive radiocoverage and a substantially wider bandwidth than the first accessnetwork. During a communication with a mobile station through the corenetwork and one of the access networks, at least one report message isgenerated including an identification of said access network independentof the identities associated with the mobile station.

Thus, a user registered in the network managed by the cellular operatorcan use the resources of the second BRAN type access network to benefitfrom the very wide spectrum offered by the BRAN and thus access thebroadband services offered by the external networks (e.g. IP networks)connected to the core network. This can be used to increase the capacityof public access to the cellular network.

The BRAN manager can be remunerated by the cellular operator for theaccess service that it provides. This is implemented simply by enhancingthe report messages circulating in the core network. Various managementmethods may then be applied between the cellular operator and the BRANmanager in order to remunerate the latter. This remuneration may helpfinancing the cost of installing the BRAN.

Another aspect of the present invention relates to a cellularradiocommunication system core network comprising switches, at least onegateway to an external network, subscriber management means and billingmanagement means, the switches being connected to a plurality of radioaccess networks each including base networks capable of radiocommunication with mobile stations, the radio access networks includinga first access network managed with the core network by a cellularoperator and at least one second access network having a substantiallyless extensive radio coverage and a substantially wider bandwidth thanthe first access network, the core network comprising means forgenerating at least one report message during a communication with amobile station through the core network and one of the access networks,which access network is identified in the report message independentlyof the identities associated with the mobile station.

Other features and advantages of the present invention will appear inthe following description of non-restrictive examples of implementation,referring to the attached drawings, in which:

FIG. 1 is a general diagram of a cellular radiocommunication systemarchitecture to which the invention can be applied;

FIGS. 2 and 3 are diagrams illustrating communications protocol stacksused in system entities of FIG. 1.

The cellular radiocommunication system shown in FIG. 1 comprises acellular network with extensive coverage, e.g. national, managed by ageneral public operator.

This PLMN is conventionally divided into a core network 21, comprisinginterconnected switches, and an access network 22 providing the radiolinks with the mobile radio terminals 23.

In the example shown, the PLMN is a second generation network of the GSMtype (Global System for Mobile communications). It incorporates a GPRS(General Packet Radio Service) type packet transmission service. In theGSM, the access network 22, called a BSS (Base Station Subsystem), iscomposed of base transceiver stations (BTS) 24 distributed over thenetwork coverage area for communicating by radio (Um interface) withmobile terminals 23, and base station controllers (BSC) 25 connected tothe core network 21 and each monitoring the base stations 24 viaso-called Abis interfaces.

Of course, the invention is applicable to other types of PLMN,especially to third generation networks of the UMTS (Universal MobileTelecommunications System) type.

The core network 21 is connected to fixed networks comprising a publicswitched telephone network (PSTN) 10 and one or more packet transmissionnetworks using respective protocols (PDP, Packet Data Protocol) such asX.25 or IP (Internet Protocol). In the example illustrated by thedrawings, there is a packet transmission network 11 consisting of theInternet.

The core network 21 comprises mobile switching centers 28 (MSC) combinedwith visitor location registers (VLR). These MSCs 28 ensure circuitswitching for circuit mode telephone or data transfer communications.Some MSCs act as a gateway with the fixed networks, especially with theswitched network 10. Each BSC 25 is connected to one or more MSCs 28 viaan interface A.

For the packet mode, the core network switches 21 are called GSN (GPRSSupport Nodes), and they communicate with each other via a so-called Gninterface.

The packet switches 30 connected to the BSCs 25 of the access network 22via a Gb interface are referred to as SGSN (Serving GSN). Some of themcan communicate with MSCs via a Gs interface for coordinating mobilitybetween the circuit and packet modes.

Other packet switches 32 of the core network 21, called GGSN (GatewayGSN), act as a gateway with the packet networks, in particular with theInternet 11. These gateways 32 are connected to the SGSNs 30 to enablemobile terminals 23 to access the Internet.

The core network 21 comprises a home location register 33 (HLR)communicating with the MSC/VLR, SGSN and GGSN through standardizedinterfaces respectively called D, Gc and Gr. The HLR is a database,located in one or more places, containing all the data specific to thesubscribers of the PLMN, chiefly their subscription, mobility andcontext details, in order to enable all the service requests relating tothese subscribers to be processed. The core network 21 may furthercomprise other units not shown in FIG. 1: short message servers (SMS),terminal registers (EIR), etc.

FIGS. 2 and 3 are illustrations of the protocols capable of being usedin packet mode communications between a mobile terminal 23 and a remoteunit such as an IP server or a user terminal accessible via one or moreIP routers belonging to the Internet network. In the Internet network12, above layers 1 and 2 of the OSI model (L1, L2), IP is used as thenetwork protocol. A corresponding IP layer is present in the mobileterminals 23 when they access the Internet. This access may take placeduring TCP (Transmission Control Protocol) sessions, or by UDP (UserDatagram Protocol) datagram exchange, to enable applications run on themobile 23 and the remote unit to exchange data.

The GPRS protocols used in the PLMN are described in GSM Recommendations03.60, 03.64, 08.16 and 09.61 published by the ETSI (EuropeanTelecommunications Standards Institute). Additional IP and UDP layers,together with a GTP (GPRS Tunneling Protocol, see technicalspecification 3G TS 29.060, version 3.4.0 published in March 2000 by the3GPP (3^(rd) Generation Partnership Project)) protocol layer, arepresent at the Gn interface, between the layer 2 and the IP layercorresponding to that of the mobile terminal 23. This Gn interface canbe carried by ATM (Asynchronous Transfer Mode) connections, with an AAL5type layer 2.

The IP datagrams exchanged by the mobile terminal 23 are encapsulated indata units of the SNDCP protocol (Sub-Network Dependent ConvergenceProtocol) which is above the LLC (Link Layer Control) protocol handlingthe addressing in packets transmitted over the radio interface. The SGSNrelays between the GTP and SNDCP protocols for transmitting thesedatagrams in the core network and to the BSS.

The BSS 22 uses the BSSGP protocol (BSS Gateway Protocol) on the Gbinterface, above the LLC layer to which it is transparent. This Gbinterface can use the frame relay (FR) technique. GSM radio protocolsare employed in the layer 1 on the Um interface, and MAC (Medium AccessControl) and RLC (Radio Link Control) protocols in the layer 2.

The invention relates to the supply of useful data for the billingmethods implemented in the core network. In the rest of the presentdescription, it is presented in its application to packet mode datatransmissions (GPRS), without this being restrictive.

In addition to the elements previously stated, the core network 21comprises one or more entities 34 called CGF (Charging Gateway Function)taking part in the billing functions in the GPRS network. On thissubject, reference can be made to technical specification 3G TS 32.015,version 3.1.1 published in March 2000 by the 3GPP. The standardizedinterface between the GSNs and the CGF is referred to as Ga. A CGFentity 34 may be incorporated into a GGSN or SGSN, or form a separateunit. It is connected to the billing system 35 used by the PLMNoperator.

Billing is based on report messages called CDR (Call Detail Report)originating from the GSNs, collected in real time by the CGF andsupplied to the billing system by the CGF after possible pre-processing.Based on these CDRs, the PLMN operator controls the billing for itssubscribers and the external operators, according to his own managementmethods.

A message called an S-CDR is opened in the SGSN at the activation ofeach context of the PDP concerning a terminal 23. Information is addedto the S-CDR when certain events occur such as an alteration in qualityof service or change in charging time slot. The S-CDR is closed anddelivered to the CGF when the PDP context is completed in the SGSN forthe subscriber. This time-stamped message indicates the identity of thesubscriber (IMSI, International Mobile Subscriber Identity) and inparticular contains the following data gathered by the SGSN:

quantities of data transmitted over the radio interface from and to theterminal, indicating the qualities of service and user protocols;

use of GPRS resources, especially regarding the mobility of theterminal;

duration of use of the PDP addresses;

indication of the terminal home PLMN, and of the visited PLMN in thecase of inter-PLMN mobility (roaming), and where necessary more preciselocation of the subscriber at the moment of creation of the S-CDR.

The SGSN may produce another message called an M-CDR for including thedata linked to mobility management protocols.

The GGSN serving the terminal may, in particular, gather the followinginformation which it similarly inserts in a G-CDR message addressed tothe CGF:

source and destination addresses;

use of external data networks;

duration of use of the PDP addresses.

The CGF 34 records the S-CDR, M-CDR and G-CDR messages delivered by theGSNs, and may possibly perform certain operations: filtering, merging,pre-processing with a view to billing, etc. It transfers the CDR data tothe billing system 35, which carries out the accounting processing.

In the system shown in FIG. 1, one or more wireless local area networks(WLAN) are connected to one or more SGSNs 30 of the core network 21.

The WLAN 40 offers a much larger bandwidth than that offered by the BSS22. But it is a short range local area network, whereas the BSS is anextensive network, with national coverage for example.

By way of example, the WLAN 40 can be of the HiperLAN/2 type. Itcomprises a gateway 41 connected to the SGSN 30 and a set oftransceivers 42 distributed in an area covered by the WLAN, whichtypically corresponds to one or more buildings.

Mobile terminals 23 held by subscribers of the PLMN 21, 22 (or of anyother PLMN with which there are roaming agreements) may, if they aremultimode terminals, also communicate through the WLAN 40. A multimodeterminal incorporates the communications protocols used in the cellularnetwork (FIG. 2), as well as those used in the WLAN. Of course, asubscriber can also own several terminals compatible with differentradio access networks.

FIG. 3 illustrates different protocols capable of taking part in anexchange of data between the Internet network 11 and a multimode mobileterminal 23 via the WLAN 40. These protocols are largely identical tothose in is FIG. 2. In the example shown, the interface between the corenetwork 21 and the WLAN 40 is also of the frame relay (FR) type, with atunnel protocol functionally similar to BSSGP for carrying the protocoldata units of the convergence layer between the HiperLAN/2 and IP (CL,Convergence Layer). The SGSN 30 performs the necessary translations fortransmitting the IP packets transparently according to the GTP protocolin the core network and according to the CL protocol to the accessnetwork.

The HiperLAN/2 system considered as an example for the operation of theWLAN 40 uses a physical layer (PHY) based on the OFDM (OrthogonalFrequency Division Multiplexing) technique. The WLAN 40 and the mobileterminal 23 also incorporate a level 2 layer called DLC (Data LinkControl) incorporating MAC- and RLC-type sub-layers. The convergenceprotocol data units are transmitted transparently by the WLAN 40, inencapsulated form in DLC protocol data units over the radio interface,and by means of the tunnel protocol over the interface with the corenetwork 21.

When a mobile terminal communicates in this way, using the radio accessresources of the WLAN 40, the SGSN 30 inserts an identification of theaccess network used into the S-CDR message, which it can simply deducefrom the physical port used for the communication to the mobile. Whenaccess is effected by means of the BSS managed by the cellular operator,the SGSN may include an indication of the same nature in the S-CDR, orthe BSS may be treated as the default access network.

Based on the access network indications used, the billing system 35 hasaccounts drawn up for calls made via the WLAN 40, for example with aview to a reversion from the cellular operator to the WLAN manager.

The WLAN manager thus acts as an alternative operator.

The same WLAN may possibly be associated in this way with several corenetworks managed by different operators.

For identifying the access network in the CDR message, a special fieldreserved for this purpose may be provided. Otherwise, fields alreadyspecified in the standard may be used, for example the “cell identity”field specified in section 6.1.1. of the aforementioned specification 3GTS 32.015.

Provision may also be made for the gateway 41 of the WLAN to be adaptedfor measuring the traffic exchanged with the SGSN 30, in order to effectlocal accounting and/or to supply the information requested for settingup the CDR in the core network 21.

What is claim is:
 1. Method for monitoring communications in a cellularradiocommunication system, the radiocommunication system comprising acore network including switches, at least one gateway to an externalnetwork, subscriber management means and billing management means, theradiocommunication system further comprising a plurality of radio accessnetworks connected to the core network switches, each radio accessnetwork including base stations capable of radio communication withmobile stations, wherein the radio access networks include a firstaccess network managed with the core network by a cellular operator andat least one second access network having a substantially less extensiveradio coverage and a substantially wider bandwidth than the first accessnetwork, the method comprising the step of generating, during acommunication with a mobile station through the core network and one ofthe access networks, at least one report message including anidentification of said access network independent of the identitiesassociated with the mobile station.
 2. Method according to claim 1,wherein said report message is generated within a switch of the corenetwork and transmitted to the billing management means.
 3. Methodaccording to claim 1, wherein the first and second access networksoperate in different frequency bands.
 4. Method according to claim 1,wherein the second access network comprises a wireless local areanetwork used for further supplying communication links independent ofthe core network.
 5. Core network for a cellular radiocommunicationsystem, the core network comprising switches connected to a plurality ofradio access networks, at least one gateway to an external network,subscriber management means and billing management means, each radioaccess network including base stations capable of radio communicationwith mobile stations, the radio access networks including a first accessnetwork managed with the core network by a cellular operator and atleast a second access network having a substantially less extensiveradio coverage and a substantially wider bandwidth than the first accessnetwork, the core network further comprising means for generating atleast one report message during a communication with a mobile stationthrough the core network and one of the access networks, which accessnetwork is identified in the report message independently of theidentities associated with the mobile station.
 6. Core network accordingto claim 5, wherein the means for generating the report messages arelocated in switches that transmit said messages to the billingmanagement means.
 7. A method of managing communications whereby usersaccess resources of a telecommunications network through facilities ofone of a plurality of access networks, the method comprising the stepsof: generating report messages for said communications, wherein saidreport message includes, for at least some of the communications, anidentifier of the access network through which the user accessesresources of said telecommunications network; processing the reportmessages to bill the users; and further processing the access networkidentifiers included in the report messages to provide remuneration of amanager of at least one of said access networks from a manager of saidtelecommunications network.
 8. The method as claimed in claim 7, whereinsaid telecommunications network uses the IP protocol.
 9. The method asclaimed in claim 7, wherein the access networks include at least onewireless LAN.